1. Field of the Invention
The present invention relates to an azo dye composition for hair dyeing that has an excellent performance as a dye for hair dyeing and proves negative in the Ames test, and also relates to a method for producing the composition.
2. Description of the Related Art
In recent years, there has been an increasing interest in the safety of chemical substances. Measures of strict legal regulation are taken particularly against production and sale of a carcinogenic substance, and it is mandatorily required to confirm that there is no carcinogenicity when developing a novel chemical substance. Although a long period and a huge cost are required for a test to determine the presence of carcinogenicity in a substance, a mutagenicity test is carried out as a test to determine in a short period and at a low cost the presence of carcinogenicity in a chemical substance. Particularly, the Ames test is broadly carried out as a method for allowing an effective screening of carcinogenicity of a chemical substance in a very simple detecting principle.
Basic Brown 16 represented by the following structural formula (I) is a useful azo dye having an excellent performance as a dye for hair dyeing. However, Basic Brown 16 is known to indicate positive in the Ames test (refer to, for example, Scientific Committee on Consumer Products. “Opinion on Basic Brown 16.” Sep. 30, 2008), and a safety problem still remains in its practical application.

On the other hand, with respect to the anthraquinone dye represented by the following general formula (II), there is a known method for obtaining a dye that proves negative in the Ames test by performing a purification operation with column chromatography (refer to, for example, Japanese Unexamined Patent Application Publication No. 11-124510).

In the formula, R represents substituted or unsubstituted alkyl, alkenyl, or phenyl.
However, the purification method described in Japanese Unexamined Patent Application Publication No. 11-124510, which can be applied in the case of the anthraquinone dye, cannot be applied to dyes such as an azo dye (refer to, for example, Japanese Unexamined Patent Application Publication No. 11-124510).
The contents of Japanese Unexamined Patent Application Publication No. 11-124510, Scientific Committee on Consumer Products. “Opinion on Basic Brown 16.” Sep. 30, 2008, Hosoda, Yutaka. Riron Seizo Senryo Kagaku, fifth edition, GIHODO SHUPPAN Co., Ltd., 1968, and “Bacterial Reverse Mutation Test.” OECD GUIDELINE FOR TESTING OF CHEMICALS, no. 471, Adopted: 21, Jul. 1997 are incorporated herein by reference in their entirety.